Films made out of polypropylene random copolymers are very common within the polymer industry and are used in applications that require superior optical properties such as gloss, transparency, surface smoothness, planarity and good tear resistance.
Films made via blown film or cast film extrusion are widely used for numerous applications, e.g. in food and textiles packaging, flower wrapping, as photo album page protectors, as coating substrates in extrusion coating processes or laminated to other materials in the formation of more complex films.
Such films are known for their easy processability and sealability. They can be produced on high-speed extrusion lines, even with low thicknesses.
Films made out of polypropylene random copolymers are also very common within the packaging industry, in various packaging techniques, like vertical and horizontal form and fill film packaging.
Said form and fill packaging is commonly applied in the food packaging, especially for the production of bags to be used for solid and/or liquid products. The bags are produced with packaging machines that simultaneously seal the bottom seam of the bag and fills it while it is in the vertical or horizontal position. Thus the sealing, while still in the semimolten/solidifying state, must be able to withstand the weight of the product introduced in the bag and generally also the pressure of air used to assist in transport of the product.
It is a constant need to improve such films in respect of sealing behaviour. This is especially true in view of constant increase of the speed of the packaging lines and consequently demanding conditions on the polymer films and their suitability for fast packaging.
To ensure fast sealing, a low heat sealing initiation temperature is of advantage. By operating at lower temperature there is the benefit of saving energy, hence economic advantages since lower temperatures are of course cheaper to generate and maintain.
There are further advantages by avoiding high sealing temperatures, especially when temperature sensitive goods are to be packed.